Process for drying raw agricultural products, particularly potatoes

ABSTRACT

A process for drying raw agricultural products for feed purposes. The raw product is first pulped into a raw and wet pulped product which is thereafter moved into a pulp box for distribution onto a roller drier. The product is heated while in the pulp box, and then distributed onto the roller drier and dried while in contact therewith. The dried product is then removed from the roller drier and is thereafter broken into flakes.

United States Patent 1191 von Nordenskjold PROCESS FOR DRYING RAWAGRICULTURAL PRODUCTS, PARTICULARLY POTATOES [75] Inventor: Reinhard vonNordenskjold, 3406 Bovenden, Germany [73] Assignee: Firma Georg Dietzel,

Deisenhofen, Germany [22] Filed: Apr. 26, 1971 [21] Appl. No.: 137,591

[30] Foreign Application Priority Data Apr. 24, 1970 Germany P 20 20074.2

[52] US. Cl. 34/12, 99/207 [51] Int. Cl. F26b 7/00 [58] Field of Search34/12, 108; 146/47;

[56] References Cited UNITED STATES PATENTS 648,248 4/1900 Edwards 34/12X 3,058,234 10/1962 Stone 99/207 X 1 July 24, 1973 3,016,936 1/1962Wilson 6131 l46/47 77,995 5/1968 Marshall 99/207 345,159 7/1886 Maull99/207 727,585 5/1903 Bunyan 99/207 1,025,374 5/1912 c6616... 34/15 x2,102,607 12/1937 Baker 34/12 x 1,977,644 10/1934 P4111611 34/12 x2,676,632 4/1954 11661 et al. 146/47 Primary Examiner-William F. ODeaAssistant Examiner-William C. Anderson Attorney-Woodhams, Blanchard &Flynn [57] ABSTRACT A process for drying raw agricultural products forfeed purposes. The raw product is first pulped into a raw and wet pulpedproduct which is thereafter moved into a pulp box for distribution ontoa roller drier. The product is heated while in the pulp box, and thendistributed onto the roller drier and dried while in contact therewith.The dried product is then removed from the roller drier and isthereafter broken into flakes.

11 Claims, No Drawings PROCESS FOR DRYING RAW AGRICULTURAL PRODUCTS,PARTICULARLY POTATOES In Germany, most eastern European countries and inthe case of our northern neighbors, almost all harvested grain and seedmust be dried artificially if a storable product is to be obtained.However, of greater importance is the artificial drying of products witha high water content, like green goods of any type, root crops, beetgreens and beet greens plus beet and, to a small extent, also corn.

Even though artificial drying experienced an enormous upswing in ourneighboring countries after the war, in the Federal Republic of Germanycorresponding efforts with respect to the artificial drying of greengoods has so far been unsuccessful because of our agricultural structurethe drying of potatoes, which had been widespread already earlier in theEast German areas, took again a considerable upswing. However, theformerly common drying on roller driers with the final product being ofa flake form is hardly used anymore, but drying in directly heated drumdriers with the final product being in a granular form, such ascoarseground corn or kernels, is used.

The following factors were mainly decisive for this change of theprocesses:

1. The flake-producing systems with roller driers which work verycarefully, particularly compared with the hot-air drying, remain at astage of development which, however, is no longer satisfactory todayboth with respect to the required capital investment expenses and alsowith respect to the current production expenses. Particularly the highportion of labor cost in the total drying expenses in the presentprocess for drying of potatoes on roller driers must be considered to bedisadvantageous. Furthermore, this process does deliver usable, however,not completely satisfactory, final products because in the case of thesteaming which is required in the present process, the potatoes areexposed to higher temperatures for a longer priod of time than isdesired and thorugh this, temperature-sensitive substances, for example,vitamins, are destroyed. Finally the steaming of the potatoes requiredby this known process causes undesired material losses and a high energyoutput.

From the above and also from the fact that the wet preservation due toits waste and unfavorable characteristics of its final product poordurability, no trade goods, feedable only by many hands and hardlyfeedable by means of automatic machines, etc. no longer meets therequirements of today, it results that a considerable need exists for adrying process which, on one hand, works just as carefully as, or evenmore carefully than, the known indirect contact drying method whichoperates with roller driers and, on the other hand, with respect to theexpenses and the losses occurring during the drying is just as favorableas, or more favorable than, the presently commonly used drying processby drying in directly heated drum driers.

Therefore, it is the purpose of the invention to produce such a processfor drying agricultural products which have a high content of water, inparticular potatoes.

This purpose is attained by a process for drying agricultural products,particularly potatoes for animal feed purposes, by drying the crushedagricultural product on roller driers, which product, if necessary, isfree from shells or skins, which process is characterized in that theproduct to be dried is crushed substantially raw and the raw, crushedproduct is then dried in the conventional manner on the roller driers.

Compared with the known method for drying agricultural products and inparticular potatoes on roller driers, the process of the invention has aseries of processtechnical advantages of which the following must benamed in particular:

1. A considerable simplification of the entire structure of the entiresystem since various operations are no longer required, for example, thetreatment in the so-called steamer. I

2. The crushing, for example, by means of crushers and pulpers which,compared with the known processes in which the goods must be shredded,are sturdy.

3. The combining of the required heat treatment and the evaporatingprocess into one single operation which takes place in only oneapparatus (roller drier).

4. By deleting the steamer, of course, the waste water problems andlosses of energy and material are also nonexistent.

5. Aside from a small amount of dust in the vapor hood, no materiallosses occur in the entire system so that this process indeed workswithout any loss."

6. The energy output for the condensate flowing out from the steamerneeded so far, is no longer required.

7. Due to the structure of the material layer on the drying rollerswhich structure, compared with the common flake production, has beenchanged advantageously, a certain output increase is obtained which morethan balances the small output reduction caused by the application ofthe cold crushed pulp onto the drier.

8. The installed system requires, with the today common constructionwhich is flush with the ground, only an area which is considerablysmaller than the area required for a comparable hot-air drying system.

9. When the only source of noise, the pulper or crusher, is sunk, theprocess operates very quietly. Since at the same time, hardly any dustaccumulates, an excellent working climate is created as can be expectedin a modern system.

From the above simplifications of the process of the invention thereresult considerable savings with respect to the investment for both themachines and also in particular the building structures and also theoperating expenses, as has already been mentioned, can be loweredconsiderably so that these drying expenses are all together evenslightly below the expenses for the drum hot-air drying.

However, it is of particular importance that the treatment of the goodsto be dried is, in the case of the process of the invention,considerably more careful than in the case of the drum hot-air dryingand that the goods are treated more carefully than in the case of theknown process for the manufacture of potato flakes, which process isalready rather satisfactory with reference thereto, since the goodsduring the process is exposed to high temperatures for a shorter periodof time and, based on the clearly defined thermodynamic relationships onthe roller drier, local overheatings can also be avoided.

The process of the invention is particularly suitable for the drying ofpotatoes which are first thoroughly washed and then are converted topulp (or crushed). The raw (uncooked) pulp can be pumped well with thehelp of a Mohno-pump in contrast to the puree from steamed potatoes Itis advisable to arrange, as a storage zone, a pulp box in front of thepump and thus also in front of the drier in order to assure an even andcontinuous processing. In order to assure a higher drying output and aneven loading of the drying roller, it can be advantageous to design thepulp box of the drier which acts also as a storage zone in such a mannerthat the pulp contained in it is already heated up to cookingtemperature. The potato puree or rather the pulp from the pulp box is,as usual, applied to the rollers whereby, however, the skin residuesadvantageously also move along into the mist or vapor phase.

The final product, which can easily be removed by knives, forms in mostcases, not large flakes, but rather granules or kernels likecoarse-ground corn. The apparent bulk density is higher than apparentbulk density of common potato flakes, which is approximately 0.25 kg./ 1tr.; however, it is not as high as the apparent bulk density of potatochips, which is approximately 0.6 kg./l tr. If at the drying of potatoesaccording to the process of the invention, the potatoes are not peeled,a gray-colored material is obtained, the coloring of which is probablypartly due to the amount of potato peels and partly due also todiscolorations which occur during the process; the latter can be avoidedto a great extent by means of a suitable machine and process structure.These are partly oxidizing processes which are speeded up catalyticallyby contact with steel, for which reason the pulper including the knivesused for the process should be made of fine alloy steel. The graycoloring can furthermore be minimized by adding common stabilizers, likemonoglycerides, sodium sulphite, milk powder, etc. to the pulp.

Furthermore a lighter final product can be obtained by peeling thepotatoes prior to cutting, crushing or pulping same, for example, byslightly steaming them in a steam peeling automatic machine so that thepeels can be removed easily and by removing the peels completely bymeans of a subsequent rewashing and, if necessary, a further washing. Inthis manner, but also corresponding to the above description, productsfor human nourishment can be produced easily by the process, since thedrier works indirectly.

As was found out through experiments, beets and green goods can also bedried by the process of the invention whereby, however, a preparation isrequired so that an incident-free and perfect application on the dryingrollers and a high drying output is achieved.

Referring to the drying of potatoes according to the process of theinvention it must further be pointed out that, as has been proven byexperiments, a surprisingly good solubility and a high degree ofagglutination can be achieved and a non-dusting (or powdery) product isobtained.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

The-embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for drying raw agricultural products for feed purposes, thesteps comprising:

pulping the raw product into a raw and wet pulped product;

moving the raw and wet pulped product into a pulp box for distributingthe raw pulped product onto a roller drier;

heating the raw pulped product while in said pulp box;

distributing the heated product onto said roller drier and dried whilein contact therewith;

removing said dried product from said roller drier;

and

breaking said dried product into flakes.

2. A process according to claim 1, including the step of peeling the rawproduct before it is pulped.

3. A process according to claim 2, including the step of crushing saidraw product prior to its being pulped.

4. A process according to claim 3, wherein said heated product is driedon said roller drier by a-contact process. i

5. A process according to claim 4, wherein said dried product is removedfrom said roller drier by a scraping knife.

6. A process according to claim 1, wherein said product is heated insaid pulp box up to a cooking temperature but said product is not cookedtherein.

7. A process according to claim 6, wherein said heated product is evenlydistributed in a layer on said roller drier.

8. A process according to claim 1, including the steps of prewashingsaid product and thereafter steaming said product prior to said pulpingstep to improve the releasability of the skin from said product.

9. A process according to claim 8, including the step of peeling saidproduct after said steaming thereof.

10. A process according to claim 1, wherein said raw pulped product ismoved to said pulp box by a pumping process.

1 l. A process according to claim 1, wherein said agricultural productis potatoes.

l I! l

1. A process for drying raw agricultural products for feed purposes, thesteps comprising: pulping the raw product into a raw and wet pulpedproduct; moving the raw and wet pulped product into a pulp box fordistributing the raw pulped product onto a roller drier; heating the rawpulped product while in said pulp box; distributing the heated productonto said roller drier and dried while in contact therewith; removingsaid dried product from said roller drier; and breaking said driedproduct into flakes.
 2. A process according to claim 1, including thestep of peeling the raw product before it is pulped.
 3. A processaccording to claim 2, including the step of crushing said raw productprior to its beiNg pulped.
 4. A process according to claim 3, whereinsaid heated product is dried on said roller drier by a contact process.5. A process according to claim 4, wherein said dried product is removedfrom said roller drier by a scraping knife.
 6. A process according toclaim 1, wherein said product is heated in said pulp box up to a cookingtemperature but said product is not cooked therein.
 7. A processaccording to claim 6, wherein said heated product is evenly distributedin a layer on said roller drier.
 8. A process according to claim 1,including the steps of prewashing said product and thereafter steamingsaid product prior to said pulping step to improve the releasability ofthe skin from said product.
 9. A process according to claim 8, includingthe step of peeling said product after said steaming thereof.
 10. Aprocess according to claim 1, wherein said raw pulped product is movedto said pulp box by a pumping process.
 11. A process according to claim1, wherein said agricultural product is potatoes.